Articles you may be interested in Effect of implanted species on thermal evolution of ion-induced defects in ZnOChemical effect of Si+ ions on the implantation-induced defects in ZnO studied by a slow positron beam J. Appl. Phys. 113, 043506 (2013); 10.1063/1.4789010Annealing process of ion-implantation-induced defects in ZnO: Chemical effect of the ion speciesWe studied the structural properties, defect formation, and thermal stability of H in hydrothermally grown ZnO single crystals implanted with Hdose ranging from 2:5 Â 10 16 to 1 Â 10 17 cm À2 . H implantation is found to create deformed layers with a uniaxial strain of 0.5-2.4% along the c-axis in ZnO, for the low and high dose, respectively. About 0.2-0.4% of the original implanted H concentration can still be detected in the samples by secondary ion mass spectrometry after annealing at a temperature up to 800 C. The thermally stable H is tentatively attributed to H related defect complexes involving the substitutional H that are bound to O vacancies and/or the highly mobile interstitial H that are bound to substitutional Li occupying Zn vacancies as the samples are cooled slowly from high temperature annealing. H implantation to a dose of 1 Â 10 17 cm À2 and followed by annealing at 800 C, is found to result in the formation of vacancy clusters that evolved into faceted voids with diameter varying from 2 to 30 nm. The truncations around the voids form more favorably on the O-terminated surface than on the Zn-terminated surface, suggesting that O is a preferred surface polarity for the internal facets of the voids in the presence of H. V C 2013 AIP Publishing LLC.
In this paper, we demonstrate industrially feasible large‐area solar cells achieving energy conversion efficiency up to 21.63% on p‐type boron doped multicrystalline Si wafers. Advanced light trapping, passivation and hydrogenation technology are used to achieve excellent light absorption with very low surface recombination velocity. The bulk lifetime of the multi‐crystalline Si wafers used for the fabrication exceeds 500 μs after optimized gettering and hydrogenation processes. The high bulk lifetime and excellent surface passivation enable Voc to exceed 670 mV. The metallization process is carried out by screen printing and firing in a conventional belt furnace. Detailed performance parameters and quantum efficiency of the cells will be illustrated in the paper. In addition, free energy loss analysis and cell simulation are also performed using the control parameters measured during cell fabrication processes.
showed a similar peak centered at 650 nm. This indicates that the PL and EL processes could be related to the same origin. Even though the center of EL peak was around 650 nm, overall EL peak showed the broad spectrum in the range of 500-850 nm. EL intensity was increased with increasing the forward voltage, as shown in Fig. 4(a). Figure 4(b) shows the light output power of Si NC LED with a SiC film as a function of the forward voltage. Light output power of the Si NC LED was measured from the topside of the Si NC LED, not from integrated measurement because it is very difficult for the total light output power from the Si NC LED to measure or calculate without a package process. With increasing the forward voltage, the light output power was linearly increased, indicating that the light emission was increased as more electrons and holes were injected into the Si NCs into a SiC film. The WPE, which means the power efficiency (output power/input power), is very important in LED applications. Based on the I-V data and light output power, the WPE of Si NC LED with a SiC film at 20 mA ($8 V) was estimated to be 1.94 Â 10 À9 %. Light output powers for the Si NC LEDs with SiC and SiN x films were almost same, which was around 0.3 nW at an input current of 20 mA. Since the forward voltage of the Si NC LED with a SiN x film was around 12.5 V at an input current of 20 mA, the input power of the Si NC LED with a SiN x film was then increased by 56% compared to the Si NC LED with a SiC film, resulting in a decrease in the WPE by 56%. Inset shows the optical microscope image of light emission from the Si NC LED measured at a forward voltage of 12 V. Because the EL peak had a relatively broad spectrum (shown in Fig. 4(a)), we think that the Si NC LED measured at voltage of 12 V showed the white light emission (shown in the inset in Fig. 4(b)). The uniformity of light emission was quite good. Based on the result of the electrical and light output performances, it was concluded that the SiC film could lead to realize an efficient Si NC LED compared to a SiN x film as a surrounding matrix including the Si NCs.In summary, a strong visible electroluminescence from Si NCs embedded into a SiC film was demonstrated. Compared to the Si NC LED by employing the SiN x film, the electrical characteristics of the Si NC LED with the SiC film were significantly improved. This was originated from a smaller barrier height for injecting the electrons into the Si NCs due to a smaller band gap of the SiC film than the SiN x film. Moreover, WPE of the Si NC LED with the SiC film was enhanced by 56% compared to that of the Si NC LED with the SiN x film. The light emission originated from the Si NCs in the SiC film was quite uniform. The results presented here can provide a very promising way to significantly improve the performance of Si NC LED.
Articles you may be interested inEffect of implanted species on thermal evolution of ion-induced defects in ZnO Ion implantation of Zn substituting elements in ZnO has been shown to result in a dramatic Li depletion of several microns in hydrothermally grown ZnO. This has been ascribed to a burst of mobile Zn interstials. In this study, we seek to understand the reason behind this interstitial mediated transient enhanced diffusion in Li-containing ZnO samples after Zn implantation. ZnO wafers were implanted with Zn to two doses, 5 Â 10 15 cm À2 and 1 Â 10 17 cm À2 . Secondary ion mass spectrometry was carried out to profile the Li depletion depth for different annealing temperatures between 600 and 800 C. The 800 C annealing had the most significant Li depletion of close to 60 lm. Transmission electron microscopy (TEM) was carried out in selected samples to identify the reason behind the Li depletion. In particular, TEM investigations of samples annealed at 750 C show significant Zn precipitation just below the depth of the projected range of the implanted ions. We propose that the Zn precipitation is indicative of Zn supersaturation. Both the Li depletion and Zn precipitation are competing synchronous processes aimed at reducing the excess Zn interstitials.Published by AIP Publishing. [http://dx.
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